12.5mpg with a split of 50/50 city/highway!!! I can't believe what I'm reading. That's horrendously bad. There's no way that's normal, something must be wrong. 100% city with hard driving, maybe, but not as you suggest. Even your signature reading of 14.6 mpg scares cr@p out of me. Seriously, something has to be wrong. Get it checked.

 

The long term data is what I am shooting for. I figure about 3000-5000 miles of research between every mod, it will be easier to do since the oil is being changed within that period. I have decided the first mod is going to be a ScanGuage II.
The good people at Scan Gauge signed on as a project sponsor and we will be using their product to monitor our MPG accurately. This is the most sensible first mod as it will tell us what's really going on, and we will be able to base our facts off of reliable readings. I am going to update the page here shortly to list the plans for mods and am still open for suggestions on what kind of mods you would be most interested in seeing.

 

That sounds good, much more thorough than I was expecting. Maybe I'm biased against people who sell intakes on car forums with false promises of power or fuel economy. Glad to hear you're planning on doing it right. Do you have winter gas in Florida?

 

I see you live in canada, I'm in upstate NY if you let your car warm up before you start driving that uses a lot of gas in the summer i was getting around 17-18 but since the winter im getting around 15 which i attribute to letting it warm up every day.

 

The Access Port can give you 1 to 2 more MPG

 

I got a smidge over 22 mpg last fill up. I'd say 70% highway/ 30% city.. moderate driving
That said, there are times where I drive it aggressive 100% city and see as low as 11 mpg.
Besides having actual problems (plugs, coils, etc.) I really think it's just a matter of driving style..
I...
premix
don't warm up, just start and go, but stay low before its all warmed up.
don't cruise in neutral. let it engine brake
keep unnecessary items out of car
anticipate lights in the city, if you know a lights changing, engine brake to appropriate speeds. stopping = use of 1st gear, idling in neutral, etc.
redlines are fun, but obviously bad for mpg
keep freeway speeds low. 85 is not low -_-

With that, I can get about 17-18 mpg with a good amount of aggressive driving.

 

Probably not, but moreover, by what stretch of the imagination is it worth it to add ~$1000 in parts to save 3 gallons of $2/gal gas?

Before going apeshit over mileage, stop and do the math on how much gas actually costing you. Let's say you drive 50 miles a day to and from work. At 13 mpg, you'd use 3.85 gallons per day. Provided you fill up at the low fuel light mark (13 gallons), you'd need a fill-up about every 3.5 days at $26/each, or $52 a week. Buy your mods, hopefully bump it up to 16mpg, and with the same math it'd be an even 4 days between fill-ups, or $43.75/week, saving you $8.25. It would take 2 years and 4 months for that "investment" to break even.

Keep in mind this is an extreme scenario- computed with the lowest typical RX8 gas mileage and an extremely optimist gain from those mods. Actual results would probably be less. It's been said before- change the WAY you drive, for free, and you'll see better gains in MPG.

 

That and winter blended gas. I started parking in a heated garage and have not seen much difference in the MPG, this would indicate most the MPG lose is due to winter blend fuel.

 

I live about a mile from the highway, and my office is about a mile off of the highway. There is a really nice entrance ramp at both ends and I pretty much pin it in every gear off the start then slow down to around 80-100 for most of the highway. About 20 miles worth. Unless of course I get a mustang trying to keep up with me through some nice high speed corners (which never happens enough), but that's a whole different story.
I did this all last summer and averaged right around 10mpg. Is it my driving style or the car? I could of swore that I did better than 10mpg when I first got the car but never really checked it. I don't know if my driving has gotten more aggressive, if the efficiency has gotten worse or if I only started paying attention to mpg when gas was over $5 a gallon.
I guess in the end it really doesn't matter. I bought the car to do 120mph around 50mph corners and my god we both (the car and I) love it sooooo much.

If someone could tell me how to get better mpg without changing my driving habits, it would really be appreciated.

 

I agree with you, it would not be worth it at all to get the mods strictly for money saving with better mpg. I really want to see what the mods do to effect the mpg, and if there is anything that works great, I will write about it in my finding and sell it on my site. If there is stuff that is claiming that it works and it does not, I will write about it in my findings and I might not sell it, or advertise it as a "saves mpg!" part. I really want to try the parts that I sell that claim to "save's mpg" and see if they work or if it is an advertising ploy. You see all the time in magazines and parts stores the "top ten tips to saving gas", lets see if they work? I want to do this and put a high performance spin on it, maybe see what saves gas as well as making our cars more fun to drive.

Surprisingly there are some RX-8 owners that want to save mpg's with their cars, my goal is to market to these people and provide them with some data and a place to buy the parts that we used on the project. I already realize that the gains will be very small from what people have experienced already in this forum. I am not expecting to see huge results, but would like to know if there is anything that works out there.

I think it is interesting to anyone that owns a sportscar, whether they care about saving mpg's or not.

Thanks for the financial look at it though, must have took a little bit of time to come up with the numbers. I will note that in my project data.

 

I feel you are going to be greatly disappointed with your research.

 

I drove out of town this last weekend and got 20.5mpg at a descent cruising speed (70+).
on the way back from my trip I got 18.5mpg but I was driving a bit faster.
I'm lucky if I get 16mpg in town although there is plenty of freeway driving.

I have 50K on the odometer. Would new plugs make a difference?

 

sure and when is the last time you cleaned your air filter?

 

change your oil

 

Racing Beat flash does not increase MPG.

Fuel Economy
We made a serious effort to look for any increase in mileage we could possibly find - but to no avail. Since mileage is the result of operation in oxygen feedback, all we had to do was change the target oxygen lambda numbers in the PCM maps and we were able to uniformly lean the mixture any time the engine was in feedback. We tried approximately 1 1/2% lean of the standard maps. As a result, we got about 1/2% improvement in the brake specific fuel consumption (BSFC - a way of measuring the efficiency of turning fuel into power) and with it some slightly rough operation. After further testing, we confirmed that for the engine as it is now configured, Mazda has already cut the mixture to maximum efficiency - it is so close to ideal there was nothing significant we could do the improve it. This was discouraging to discover, but common sense says Mazda tried very hard to optimize fuel mileage - and our findings confirmed this

Here is a scan of my 06 owners manual

How you operate your Mazda dete
how far it will travel on a tank of fueL
these suggestions to help save money
fuel and repairs.

·Avoid long warm-ups. Once the e _
runs smoothly, begin driving.
·Avoid fast starts.

·Keep the engine tuned. Follow the
maintenance schedule (page 8-3)
have an Authorized Mazda Dealer
perform inspections and servicing.
·Use the air conditioner only when
necessary.
·Slow down on rough roads.
·Keep the tires properly inflated.
·Don't carry unnecessary weight.
·Don't rest your foot on the brake
while driving.
·Keep the wheels in correct ali5~~-
·Keep windows closed at high sp

·Slow down when driving in cros
and headwinds.



The price of a replacement air filter is close to 30 USD. Hell for 50 USD I can get a K&N and use it for the life of the car with regular cleanings. Not sure how much the cleaning kit is. I bought one three years ago for my truck and haven't used it up yet.

My 8 is up to date with all flashes and I premix. City MPG is 18 with some aggressive driving daily.

 

Don't forget new coils from BHR, they may help due a hotter spark.

We have no data on this.

 

I have a K&N and it was cleaned and oiled recently. I change my oil as well as add oil when needed. I did change my spark plugs not long ago with some off of my friends 84 RX-8 parts car. They were in good shape while mine looked like a steak had been grilled on them. The 84 uses four which look identical to the 04 leading so we used them for trailing also. No increase or decrease in mpg but it did seem to run much better. I'll probably put the plugs "designed" for my engine on eventually but doubt it will make a difference.

 

I am going to install my turbo xs midpipe combined with my hks hi power I have a long drive out to Denver this Thursday. my plan is to record mpg going different speeds with the midpipe on and see what I get. before I was getting 23 hwy 18 city. I just did a fresh oil change last night and I will have some unnecessary crap in the car like fluids, water, clothes, and some gifts.

I hope to attain 25 mpg or more going 65 and 23 mpg going 75 and 20 mpg going 85

I know that opening up the exhaust system can result in better mpgs on pistons I just don't know if it will do the same on a rotary. I'll keep you all updated, wish me luck!

 

change yrou coils thats what did it for me I was getting 16mpg I changed my coils and it shot up to 23 mpg on the hwy

 

I've come to realize that my MPG is very close to stock and unless it drops from the almost 16 city / 22 Hwy. After all those are the EPA numbers. I've gotten 18 highway driving 85 and and fighting traffic. Driving 70 with less changes in throttle position I get 22. I don't believe in spending 100s for minor gains. I only have 53K miles so coils are in the future.

 

that's pretty average mpg I'd say your doing great.

 

What kind of coils did you use? OEM or aftermarket? I am interested in eventually replacing mine for my mpg project research and would like to know what you used to get those results.

 

DIY: How to Fix your MPG "Problem"

Step 1. good maintenance
step 2. shift at 2.5k
step 3. notice your 20mpg and be amazed.

 

I am anxious to see what results you see from the mid pipe in addition to your cat back. Did you see any mpg gains from just the cat back addition? Also, do you have any other mods besides the exhaust and coils done to your car that could be contributing to your abnormally high 25 mpg results? Sorry for all the questions, I am doing some parts research for my mpg project with my 8 and am amazed at your mpg findings.

I am not sure which way your driving to denver, east or west, but try and get your mpg readings on flat stretches of road. One of the many things I learned from my Scangauge II is that increases in engine load result in decreases in mpg's, such as driving uphill.

FWIW, I have been monitoring my mpg's in my 100% stock 07 RX-8 for about 3 months with my scangauge II and by the trip meter in the car and have never above 22 on the tank average. It is always between 20 and 21 mpg, regardless of highway time. We drive it semi aggressive too, but not to the point of red lining everywhere.

If you can, pm me or provide your results when your research is complete.

 

I haven't gotten the 25mpg yet I was hoping to get there, the best I had was slightly over the 23 mpg mark traveling north to south with light traffic.

Unfortunately I did not have all the bolts I needed for the mid pipe so that fun project is on hold.

I will update you all later. i imagine my mpg will be increased slightly on my trip out and decreased on my trip back. I am heading west to east.

Wish me luck!